The present invention relates to a hydraulic control system for a continuously variable V-belt transmission.
In the case of a continuously variable V-belt transmission resulting from combining a continuously variable V-belt transmission mechanism with a multiple plate wet type starting clutch, the continuously variable V-belt transmission is controlled to provide the largest reduction ratio upon starting a vehicle. This is because if the starting clutch is engaged with a small reduction ratio, a sufficiently large traction force can not be produced, resulting in stalling of the engine. However, since the conventional hydraulic control system is not equipped with a maximum reduction ratio maintaining valve that puts the continuously variable V-belt transmission mechanism into the largest reduction ratio upon starting the vehicle irrespective of the state of a shift control valve, it has been difficult to start the vehicle if the shift control valve goes out of order and fails to puts the transmission mechanism into the largest reduction ratio state.